Directly plugging my Martin SWDGT with K&K Pure Mini pickup into a PA doesn't sound good, at least in my limited experience. I put a preamp in between - the Fire Eye Red Eye - and plug a tuning pedal into its effect loop. That combo has worked pretty well so far. The Red Eye has a volume boost button, which is super handy for being heard better during solos (I play in a bluegrass band). None of the folks I know who play acoustic instruments plug directly into a PA, except for one of my banjo playing friends (I guess it works for that since you can't mess up a banjo sound anyway
). They all use some kind of DI box/preamp/equalizer device, which has a HUGELY positive effect on tone. From what I gather, the Baggs Venue is a great option, or the Baggs DI. I like my Red Eye quite a bit. It's super tiny and makes a great tone. I am being told that one has to try a bunch of different devices because each guitar/pickup combo is different and different people prefer different types of tone, obviously.